Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21D
SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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23/00
Mine roof supports for step- by- step movement, e.g. in combination with provisions for shifting of conveyors, mining machines, or guides therefor
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E21D23/0004
along the working face
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E21D23/0008
comprising a pair of joined struts
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